Accessing underground assets can be difficult. Structures on the surface can block access and underground assets can be buried up to 20 metres below the surface. Even locating assets from the surface can be challenging. McAllister Specialist Construction can assist in remote surveying of your underground assets through a range of methods.

Once we have located your underground pipeline and sewer assets, the next step is to access them. We have a variety of ways to assist including:

  • Shaft construction

  • Pipe jacking

  • Timber heading

Read on below to learn more about our specialist services, or get in touch and talk to the experts today

Shaft construction

McAllister Specialist Construction has extensive experience building segmental caisson shafts for vertical underground access directly on top of the target pipeline. We can sink these shafts in various ways – the method we choose depends on the ground conditions. In hard ground or solid rock, we construct the shaft using an underpinning method with the segments grouted in place as we assemble each ring. We can also sink or hydraulically jack the shaft through the strata with a cutting shoe until we reach the pipeline or close enough to expose it and provide structural support before gaining access.

Pipe jacking

Pipe jacking is primarily used for horizontal access to underground assets when vertical access is not possible. We sink a shaft to the same level as the target pipeline before installing a pipe jack to reach it. Jacking pipes come in two categories – reinforced concrete and glass reinforced polyester (GRP). We select the right one for the specific ground conditions. We hydraulically jack this pipe into position through carefully controlled excavation at the tunnel face.

Timber heading

Timber heading is a traditional hand mining technique. We use this method when the ground conditions are suitable - such as London clay. A timber frame supports the earth above and the heading is grouted into place as the tunnelling advances. Hand mining techniques such as this allow for greater accuracy when working close to critical sub-surface infrastructure.